Anything you like! I did skipping, squats and shoulder rolls, then we had to do some dead-lifts to warm up for the WOD.
21 Dead-lifts (15kg in plates and then whatever the bar weighs, could have gone heavier though)
21 Chin-ups (Using a blue and a red band - which are these giant rubber bands to help counter-balance your body weight if you can't do unassisted chin-ups)
21 Sit-ups (I was just using an ab-mat but everyone else was doing GHD situps http://www.youtube.com/watch?v=Ufaa41nkIP8)
So in total 1.6km run, 90 Dead-lifts, 90 Chin-ups and 90 Sit-ups!!
Then the trainer made me practice my double-unders cuz I can't even do one.. and still can't! I think I'll have to buy a skipping rope and practice, although that's not really going to work in the flat so I'm going to have to look dumb in the local park or something!
I didn't have a issue with the run, the dead-lifts or the sit-ups (although I had to take breaks) but the chin-ups weren't good. My form was dreadful, but to be fair the most chin-ups I've ever done in my life is probably 10!!
Today I can't lift my left arm above shoulder height and my right bicep and forearm are sore, tomorrow is going to be hell I reckon!! Luckily I'm not going again til Monday so I'll have time to recover.
This chick is one of the trainers: http://games.crossfit.com/features/videos/im-really-happy-amy-dracup, if I can end up looking even half like that I'll be happy!